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Etching
involves the selective removal of material from a sample by chemical or
physical means. It is a "reverse growth" process in which surfaces of lowest
energy tend to be the most stable and regions of lattice distortion tend
to be more susceptible to removal. The technique is used to reveal the
microstructure of sample surfaces. It is also employed to prepare surfaces
for other treatments. Etching techniques include: Chemical etching, electrolytic
etching, thermal etching, plasma etching, and preferential oxidation. The
diagrams illustrate the effect of surface etching on surface texture and
reflectivity, and show optical photomicrographs of the samples. The left
diagram illustrates the effect of crystallite orientation on etched roughness
and reflectivity. The right diagram illustrates preferential attack at
grain boundaries and the local change in surface slope that this produces. |
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